Harold S. Black, while working at Bell Labs, changed the design world when he published his work on feedback in “Stabilized Feed-Back Amplifiers” in the January 1934 issue of Electrical Engineering, published by the American Institute of Electrical Engineering. This work is also memorialized as U.S. Pat. No. 2,102,671, filed Apr. 22, 1932. Since then, legions of designers have employed negative feedback to produce everything from hearing aides to camera controllers for Jupiter probes.
What is needed are methods and apparatus for calibration of a feedback path to achieve improved performance, especially as it relates to improving the Power-Supply Rejection Ratio (PSRR) of a circuit structure having differential feedback; and specifically for calibrating the gain-balance of the differential feedback path so as to optimize PSRR.